Centrifugal pumps are used in a wide variety of applications, including well related applications. For example, centrifugal pumps are used in electric submersible pumping systems deployed in wellbores to produce or otherwise move fluids in the wellbore. Centrifugal pumps are constructed with stacks of alternating impellers and diffusers that cause fluid to flow from an inlet of the pump to an outlet. The impellers are rotated by a shaft and impart motion to the pumped fluid via pump impeller vanes. As fluid passes from each impeller flow passage, the fluid is routed through a diffuser passage to the next impeller and ultimately to the outlet.
Many centrifugal pump designs have inefficiencies due to significant fluid separation losses. For example, centrifugal pumps with radial vane configurations suffer from excessive diffusion in the ducts connecting vaned passages. Excessive diffusion can occur in the flow passages between the diffuser blades or impeller blades, but the excessive diffusion also can occur in the transition region from the trailing edge of the diffuser to the duct leading to the exit of the diffuser. Another location susceptible to excessive diffusion is the transition region from the entrance of the impeller inlet duct to the leading edge of the impeller blade.
In some radial type stages, the trailing edge of the diffuser blade has been formed as a thick, blunt member to control excessive diffusion within the diffuser flow passage, however this approach leads to large amounts of diffusion and separation losses in the duct just downstream of the diffuser trailing edge. An alternative approach has been to form the trailing edge of the diffuser as a relatively thin member to minimize the area change at the duct transition, however this approach leads to excessive diffusion of the flow in the diffuser passage.